The present invention relates to a control method of an apparatus for data recording and reproducing for information interchange, more particularly it relates to a control method of a disk drive for an optical recording/ reproducing disk.
Two different types of optical disks for information interchange are well known in the prior art. One is the optical disk in which users can only reproduce prerecorded information and cannot record any information thereon, such as ROM (Read Only Memory) type optical disk. The second is the optical disk in which the users, can not only reproduce but also record information. Hereinafter, the latter is called "recordable" optical disk.
An example of an assembly diagram of a disk drive for a recordable optical disk is shown in FIG. 1.
In FIG. 1, the recordable optical disk is exampled by a Write Once Read Memory (WORM) type optical disk (1). The optical disk 1 comprises recordable disk medium with a large storage capacity, whose storage capacity ranges from several hundred Mega Bytes to several Giga Bytes per disk. In this kind of optical disk, defect are inevitable in the recording area; thus defect management is necessary. For this purpose, the defect management information is also recorded in the assigned area of the optical disk (1). The defect management information designates addresses of defective sectors and alternative sectors which store the information intended for the defective sectors. A loading mechanism (3) of a disk drive (2) sends an optical disk to recording/reproducing apparatus (4) in the disk drive when the optical disk is inserted to the disk drive (2), and also automatically ejects the optical disk from the disk drive (2) when the optical disk is released from the recording/reproducing apparatus (4). A recording/ reproducing apparatus (4) records and reads information on the optical disk which is set thereto by loading mechanism (3).
A controller (5) comprising a microprocessor controls the recording/reproducing apparatus (4) so as to record information transferred from a host computer (6) on the optical disk and/or reproduce information. The reproduced information is transferred to the host computer (6) from the optical disk in response to a command from the host computer (6) through an interface (7) such as Small Computer System Interface (SCSI). The controller (5) also controls the loading mechanism (3). A Random Access Memory (RAM) (8) is included in the controller (5) to store the defect management information of a loaded optical disk.
In the arrangement as shown in FIG. 1, when an optical disk is inserted to the disk drive (2), the loading mechanism sets it into the recording/reproducing apparatus (4). Then, the controller (5) actuates recording/reproducing apparatus (4) to read out all of the defect management information which have been recorded on the assigned area of the optical disk, and causes the information to be stored in the RAM (8) in the controller (5). Thereafter, when the controller (5) receives a command from the host computer, it judges on the basis of the defect management information in the RAM (8) whether an indicated sector is defective, in which case the controller indicates the address of the alterative sector, for the indicated sector, to the recording/ reproducing apparatus (4). When the controller receives a command to record information in a sector on the disk and a recording error occurs in the sector, the same information being recorded in the sector is recorded again on an appropriate a corresponding alternate sector in an alternate area determined by the defect management information in the RAM (8). The controller then updates the defect management information of the RAM (8) to represent the most recently detected defect.
As described above, the conventional control method of the disk drive for an optical disk requires a predetermined procedure comprising the steps of: setting an optical disk to the recording/reproducing apparatus (4), reading out all of the defect management information which were recorded beforehand on the optical disk, and executing commands for indicating read-out and write-in, which are transferred from the host computer (6). In this method, extra time for reading out all of the defect management information is required, which effects start up time between completing the predetermined procedure from loading the optical disk and executing the first command.
The above disadvantage of the conventional method will be described hereinunder in detail.
An example of the conventional defect management method for a Write Once Read Memory type optical disk of 130 mm in diameter is shown in FIG. 2. There are 20,000 tracks to be assigned to the disk, which are numbered as No. 1 to No. 20,000. A track is divided into 32 sectors, and each sector has a memory capacity of 512 bytes.
The user area is a memory area, which constitutes a majority of the memory, for users to record/reproduce data on the disk. An alternative area is a memory area to store data which was originally intended to be recorded in a user area, but was judged as defective by a verify-read user area, operation just after recording the data on the user area. Herein, the defective sector is a sector in which quality of signals reproduced therefrom can not reach a predetermined level due to various errors caused by small defects on the optical disk. A map area is a memory area to store the defect management information, indicating which sectors in the user area correspond to sectors in the alternative area.
Further, a data storage area of the optical disk can be divided into plural bands, for example, 63 bands at maximum. Each band comprises a map area, an alternative area and an user area. However, some bands have no user area as described hereinafter. Four tracks in each band (128 sectors) are assigned to the map area and the alternative area respectively, but the number of tracks assigned to the user area is not fixed. Also, it is not specified as to which type of area is located in each band. These parameters can be arbitrarily determined by the users, or can be automatically assigned by the controller in the disk drive. To store the parameters thus determined, a control track is prepared in a specified area which is different from the track areas corresponding to track No. 1 to 20,000.
FIG. 2 shows an example of a format for band division and track numbering in each area. The data storage area of the optical disk is divided into 63 bands of #1 to #63. In this example, each of the bands of #1 to #62 has a user area, and the band #63 has no user area. Each user within bands of #1 to #61 includes 314 tracks, and band 62 includes 342 tracks to adjust a fraction of tracks.
When data is recorded on a sector in the user area of the band #1 and sector has been judged as a defect sector, at the verify read immediately after recording the data. The same data are recorded again on a sector with the foremost address in the alternative area of the band #1 in which data have not yet been recorded. The alternative sector in the alternative area is verified, and the data is recorded on a second alterative sector, if the first alternative sector is judged defective. As above described, the same data is recorded again and again on a different alternative sector until the judgment of the verify-read becomes "not defect" in an alternative area of band #1. As a result, each defective sector in the user area of the band #1 is assigned a sector in the alternative area of the band #1 in a ratio of one to one. The addresses of each defective sector and corresponding alternate sector constitute one data pair within the defect management information. This data pair is recorded at the foremost sector within the map area of band #1, at which--. data have not yet been recorded. Hereafter, this foremost sector will be referred to as the last sector, which signifies the most recently recorded data pair, but not necessarily the last sector in the map area. The sector at which the defect management information is stored in the map area is verified, of course, and the same process as described above is repeated when the sector is judged defective. For the map area, the same data pair is repeatedly recorded on the subsequent sector, until the judgment of the verify-read becomes "not defective" in the map area of the band #1.
The same process as described above is repeated for the bands from #2 to #62. The band #63 is prepared for shortage of memory in the alternative area and/or the map area in the bands from #1 to #62 due to overflow caused by too many defect sectors therein. Therefore, band 63 has no user area.
Next, the map area will be described in detail. Each sector of the map area, which comprises 512 bytes, is divided into 128 fields each consisting of 4 bytes. Three bytes in each field designates the address of a defective sector in the user area and the remaining one byte designates the address of an alternative sector in the alternative area for which the defective sector is alternated. Accordingly, information in each sector of the map area can represent 128 defect management information data pairs at maximum, the number of which is equal to the number of sectors in the alternative area assigned to one band. As a result, one sector in the map area can store all of the defect management information for the band. In the case of data overflow in each band, the band #63 is prepared to store overflowed data.
For the Write Once Read Memory type optical disk, the recorded cannot be erased to use the same storage area again. Whenever a defective sector occurs in a band, one sector in the map area of the band is used to store the defect management informations for the defective sector. When a defective sector occurs in a band for the first time, defect management information represented with 4 bytes is stored on the first field of the first sector in the map area of the band. For the next occurrence of a defective sector in the same band, the defect management information for the first defective sector is stored again on the first field of the second sector in the map area of the band. Defect management information for the second defective sector is newly stored on the second field of the second sector, because the defect management information recorded on the first sector of the map area cannot be amended.
As is described above, the latest defect management information is stored on the last sector. In other words, the defect management information, representing the currently known list of defective sectors, is stored in the map area sector most recently recorded.--; Only the latest defect management information is required for reading data out of the user area and for writing new data to the user area, because it is not aware that on which sector in the alternative area the new data should be recorded again when a defect sector occurs, and because it is not aware that in what address of a sector the next defect management information should be stored.
Due to these facts, when the optical disk is loaded in the disk drive, the following procedure is required:
first, the information on the control track is read to confirm the tracks at which the map area of each band is located,
secondly the last sector which have been already used in all of the map areas in all of the bands are found out to read all of the latest defect management information, and
thirdly the latest defect management information for all of the bands are transferred to store in the RAM of the disk drive.
Next, time required for reading out a defect management information will be described hereafter. Assuming a rotational speed of an optical disk is 1,800 r.p.m., it takes 33 msec per revolution. When the map area of each band is mostly used, it cannot be expected to save time by searching area of the next band immediately after reading the latest defect management information stored on the last recorded sector in the current band. In such a case, the whole map area is read one by one with the rotation of a disk. As the total number of tracks assigned to all map area is 252, it takes 8.4 seconds to read the whole map area.
The optical disk system has a great advantage that the optical disk is exchangeable. However, as described above, it takes more than 8 seconds every exchange to read the defect management information, so that the conventional optical disk system has a problem that a time required for reading out all the defect management informations is superfluously added to the time required for loading an optical disk.